Device for purifying exhaust gases

ABSTRACT

Device and method for purifying exhaust gases from motor vehicles. A housing includes an intake opening, an outlet opening, an exhaust gas inflow area, an exhaust gas outflow area, and a longitudinal axis. At least one module for purifying exhaust gas is arranged in the housing and has a module axis. The at least one module connects the exhaust gas inflow area and the exhaust gas outflow area, and the module axis is tilted relative to the longitudinal axis of the housing. The instant abstract is neither intended to define the invention disclosed in this specification nor intended to limit the scope of the invention in any way.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119 of AustrianPatent Application No. A 169/2005, filed on Feb. 2, 2005, the disclosureof which is expressly incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a device for purifying motor vehicle exhaustgases. The device includes a housing with an intake opening and anoutlet opening, and at least one module for purifying exhaust gasarranged in the housing and connecting an exhaust gas inflow area and anexhaust gas outflow area.

2. Discussion of Background Information

Motor vehicle exhaust gases that are emitted unpurified or littlepurified from automobiles and commercial vehicles during their operationare considered to be one of the main causes of environmental pollution.Therefore, in many nations and regions, attempts are being made tocombat this adverse pollution load on the environment that is on therise. This is being accomplished statutory measures, for example byimposing maximum permissible pollutant levels for exhaust gases frommotor vehicles.

Since the maximum pollutant levels for exhaust gases are regularlyfurther lowered with new statutory measures or standards, there is aconstant requirement on the part of automobile manufacturers to purifyexhaust gases from motor vehicles better or more effectively. Intensiveefforts are therefore being made to increase the efficiency ofpurification modules for motor vehicle exhaust gases.

The efforts have hitherto been directed at increasing an efficiency orpurification effect of modules for purifying motor vehicle exhaust gasesby improving a quality of the modules. This is accomplished, forexample, by applying more effective catalysts for converting nitrogenoxides or by more effective particulate filters.

Modules for purifying motor vehicle exhaust gases are provided in theexhaust trains of motor vehicles. Particulate filters can be installedin the housings of rear mufflers that are easily accessible, providing asimple retrofit of motor vehicles supplied without particulate filters.Two problems are associated with such retrofits, however. First,installation space is limited for modules to be retrofitted. Second, itis not possible to install any desired number of modules one behind theother, because then such a high pressure is built up at the modulesarranged between the exhaust gas inflow area and the exhaust gas outflowarea that a motor performance decreases. To put it differently: aninstallation space and a reliable pressure difference between exhaustgas inflow area and exhaust gas outflow area are predetermined.

SUMMARY OF THE INVENTION

Recognizing these problems, the present invention relates to a devicefor purifying exhaust gasses from motor vehicles that provides a greatvolume of modules for purifying while taking into account installationspace and reliable pressure difference.

This is attained with a device where the module(s) is/are arrangedtilted towards a longitudinal axis of the housing. Advantageousembodiments of a device according to the invention are described.

An advantage achieved with the invention is that, even taking intoconsideration a reliable pressure difference between a tiltedarrangement of the module(s) relative to a longitudinal axis of thehousing, larger modules can be accommodated in the housing than with anarrangement perpendicular to the longitudinal axis. Module volume, or acatalytically effective or filter-active module surface, is thusmaximized and utilization of a predetermined volume of the installationspace is improved. The length of a flow path from exhaust gas inflowarea to exhaust gas outflow area can be kept constant compared to anarrangement of the module(s) perpendicular to the longitudinal axis.Flow cross section is increased despite increased module volume. Areduction of pressure difference between an exhaust gas inflow area andoutflow area occurs.

In a preferred embodiment, the module is tilted at a tilt angle of 15°to 75° relative to the longitudinal axis of the housing. In this rangeof tilt angle, an advantageously effective increase in the modulesurface can be achieved with good flow over the module front sides byexhaust gas.

In a preferred embodiment, the housing is essentially cylindrical. Ifthe cylindrical housing has an intake opening on the front and an outletopening on the end (for example, if the device is a muffler), then themodule(s) can be arranged essentially over an entire length of thehousing.

According to the invention, the module is made at least partially ofmetal foam. When exhaust gas flows through metal foam, due to alabyrinthine pore structure of the metal foam, a homogenization of theexhaust gas flow occurs over its cross section and any inhomogeneitiescan be offset. The invention provides modules with several connectedlamellar filter and catalyst elements, with an element of a pure metalfoam facing towards the exhaust gas inflow area. The metal foampreferably has a porosity of 80 to 98% and a pore size of 4 to 30 ppi(pores per inch). Downstream catalyst and/or filter elements of themodule may include metal foam, or at least have such as a substrate forcatalytically active substances. In this case, a well-balanced flowdistribution and flow speed result in the module, and pressure andtemperature inhomogeneities are effectively counteracted.

The module may comprise several filter elements and/or catalyst elementsin order to purify as completely as possible the exhaust gas guidedthrough the module.

One or several modules spaced apart from one another can be arranged ina device according to the invention in order to optimize an exhaust gasflow within the housing.

An advantageously large inflow surface for exhaust gas is given if, in across-sectional view, the module covers the entire cross section of thehousing.

In an embodiment of the invention, the module is connected to thehousing. For example, with corresponding sizing, the module can beclamped in the housing. This approach is suitable in particular for aretrofit of motor vehicles, because expenditure for retrofitting modulesfor purifying exhaust gases can be kept low. However, it is alsopossible to connect the module to the housing in another way, e.g., bymetallic connection such as welding or soldering or indirectly by aswelling mat.

In another embodiment, the module is kept spaced apart from the housingby a gas-tight support element connected to the housing. The modulepenetrates the support element in order to provide a gas flow betweenexhaust gas inflow area and exhaust gas outflow area. In particular,when several modules are provided, a support element allows individualmodules to be adjusted as needed and adapted in their alignment to theflow conditions within the housing or the device.

The support element is preferably a metal plate due to thermal andmechanical loadability of the support element and in order to keep thespace necessary for the support element small.

The module(s) can be of any geometric shape. A cylindrical embodiment ispreferable in terms of flow technology. An arrangement in the supportelement is then made such that the module penetrates the support elementwith a module longitudinal axis. Accordingly, the modules are encased ina gas-tight manner in some areas so that exhaust gas must flow throughthe module completely after entering the exhaust gas inflow area.

According to the invention, the support element is installed in thehousing such that the exhaust gas inflow area is conically tapering inthe direction from the inlet opening to the outlet opening. Through thisgeometric design, the flow conditions in a cylindrical housing are suchthat the exhaust gas inflow area has a large cross section area near theinlet opening where there are large exhaust gas volumes. Due to thistapering, the exhaust gas inflow area has a small cross section at apoint where a small exhaust gas volume is given, because a large amountof the exhaust gas has already flowed into the module(s). The localvolume conditions of the exhaust gas inflow area are thus adjusted in atargeted manner to the locally given exhaust gas volumes. As a result,all module areas or all modules are flowed over or loaded approximatelyequally and virtually the same pressure and temperature conditions areachieved in the entire module or the individual modules.

At least one flow guidance device (e.g., a baffle plate) can be providedin order to provide a uniform flow of exhaust gas over the module(s).

Further advantages and effects of the invention result from the contextof the specification and the exemplary embodiments.

The present invention is directed to a device for purifying exhaustgases from motor vehicles that includes a housing including an intakeopening, an outlet opening, an exhaust gas inflow area, an exhaust gasoutflow area, and a longitudinal axis. At least one module for purifyingexhaust gas is arranged in the housing and has a module axis. The atleast one module connects the exhaust gas inflow area and the exhaustgas outflow area, and the module axis is tilted relative to thelongitudinal axis of the housing.

According to a feature of the invention, the module axis can be tiltedat an angle of 15° to 75° relative to the longitudinal axis of thehousing.

In accordance with another feature of the present invention, the housingmay be substantially cylindrical.

According to still another feature of the instant invention, the devicecan be a muffler.

Moreover, the at least one module can be at least partially made ofmetal foam.

Further, the at least one module may include at least one of: at leastone filter element and at least one catalyst element.

According to another feature of the invention, the at least one modulemay include several modules that are spaced apart from one another.

In accordance with a feature of the invention, the at least one modulecan cover an entire cross section of the housing.

According to still another feature, the at least one module may beconnected to the housing.

Further, a gas-tight support element may be connected to the housing tomaintain the at least one module in a spaced apart relationship from thehousing. The at least one module may penetrate the support element toallow the exhaust gas to flow between the exhaust gas inflow area andthe exhaust gas outflow area. The support element may be a metal plate.Further, the at least one module can be substantially cylindrical andpenetrate the support element with the module axis. The at least onemodule can include plural modules encased in a gas-tight manner in someareas. The support element may be connected to the housing such that theexhaust gas inflow area is substantially conically tapered in adirection from the intake opening to the outlet opening.

In accordance with still another feature, the device comprises at leastone flow guidance device. The flow guidance device can include a baffleplate.

The present invention is directed to a method of purifying exhaust gasesof motor vehicles. The method includes directing exhaust gas through aninlet opening of a housing, purifying the exhaust gas in at least onemodule arranged in the housing, in which the at least one module has amodule axis tilted with respect to a longitudinal axis of the housing,and directing the exhaust gas through an outlet opening of the housing.

According to a feature of the invention, the module axis can be tiltedat an angle of 15° to 75° relative to the longitudinal axis of thehousing.

In accordance with still yet another feature of the present invention, agas-tight support element can be connected to the housing to maintainthe at least one module in a spaced apart relationship from the housing,and the at least one module can be supported to allow the exhaust gas toflow between the exhaust gas inflow area and the exhaust gas outflowarea. The support element may be arranged in the housing to form aconically tapered exhaust gas inflow area.

Other exemplary embodiments and advantages of the present invention maybe ascertained by reviewing the present disclosure and the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is further described in the detailed descriptionwhich follows, in reference to the noted plurality of drawings by way ofnon-limiting examples of exemplary embodiments of the present invention,in which like reference numerals represent similar parts throughout theseveral views of the drawings, and wherein:

FIG. 1: A section through a device having a single module;

FIG. 2: A section through a device according to the invention with fivecylindrical modules; and

FIG. 3: A cross section through a device according to the invention withmodules having several different catalyst and filter elements.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

The particulars shown herein are by way of example and for purposes ofillustrative discussion of the embodiments of the present invention onlyand are presented in the cause of providing what is believed to be themost useful and readily understood description of the principles andconceptual aspects of the present invention. In this regard, no attemptis made to show structural details of the present invention in moredetail than is necessary for the fundamental understanding of thepresent invention, the description taken with the drawings makingapparent to those skilled in the art how the several forms of thepresent invention may be embodied in practice.

FIG. 1 shows a device 1 according to the invention, which has anelongated cylindrical housing 2 with an inlet opening 3 formed thereonand an outlet opening 4. In the housing 2, several lamellar orplate-like elements of a module 7 are inserted or clamped such that asurface of the individual elements flowed over or a module axis X, whichcorresponds to a perpendicular to the parallel surfaces of the layers,is tilted relative to a housing longitudinal axis Y. Depending on thedesired purification effect, the individual lamellar elements of themodule 7 can be catalyst or filter elements and are all composedessentially of a metal foam that optionally bears a catalytically activesubstance or is coated therewith. Furthermore, an open-pore metal foambody 8 is provided. As can be seen from FIG. 1, the individual elementsof the module 7 are sized such that essentially the entire free crosssection of the housing 2 is covered crosswise to the housinglongitudinal axis Y.

Exhaust gas enters through the inlet opening 3 into an exhaust gasinflow area 5 within the housing 2. The exhaust gas first flows overmetal foam body 8 and then over the downstream elements of the module 7.The exhaust gas then reaches the exhaust gas outflow area 6 andsubsequently exits, purified, through the outlet opening 4.

A pressure difference between exhaust gas inflow area 5 and exhaust gasoutflow area 6 is determined by the length of a minimal flow path L forthe exhaust gas through the connected elements of the module 7. Comparedto a conventional arrangement where modules are arranged with a moduleaxis that is parallel to the housing axis, the tilted arrangement of theinvention provides that the length of a minimal flow path L can be keptthe same with simultaneous enlargement of a gas entry surface 14 andwith an increase of a module volume. That is why both an improvedpurification effect and a low pressure difference between exhaust gasinflow area 5 and exhaust gas outflow area 6 can be achieved with adevice 1 according to the invention.

FIG. 2 shows a section of a second exemplary embodiment of the deviceaccording to the invention. Several cylindrical modules 7 areaccommodated in a support element 11 in a cylindrical housing 2. Housing2 has an inlet opening 3 and an outlet opening 4 for the exhaust gas.The support element 11, together with the modules 7, separates anexhaust gas inflow area 5 from an exhaust gas outflow area 6. Thesupport element 11 is disposed in the housing 2 in the direction fromthe inlet opening 3 to the outlet opening 4 such that the exhaust gasinflow area 5 is conically tapering, and the complementary exhaust gasoutflow area 6 is conically widening. This subdivision of the housingvolume provides that the individual modules 7 are flowed over and loadedequally with respect to the exhaust gas volume and flow speed.Furthermore, the individual modules 7 reach approximately the sametemperature in operation, which has a favorable effect with respect toan approximately equal purification effect of the modules 7.

The exhaust gas flow is shown in more detail in FIG. 3. FIG. 3 shows asection of a device 1 according to the invention with a total of fourmodules 7. The modules 7 are arranged in a lamellar manner, eachrespective module 7 having one gas entry surface 14, one gas exitsurface 15, a metal foam body 8, a catalyst element 9 and a dieselparticulate filter 10.

Still referring to FIG. 3, each module 7 has a module axis X that isperpendicular to the surfaces of the lamellar elements of the module.Similar to that shown in FIG. 2, the modules are arranged at a tiltangle a relative to a longitudinal axis Y of the housing 2 and held bysupport element 11. The tilt angle a shown in FIG. 3 is approximately60°. Exhaust gas inflow area 5 and exhaust gas outflow area 6 aredivided into two essentially conically tapering or diverging volumesthrough the arrangement of the support element 11. In order to ensurethat exhaust gas can flow only through the modules 7, they are connectedto the gas-tight metallic support element 11 via likewise gas-tightconnection points 13 and respectively provided with a gas-tight jacket12. In this way, inflowing exhaust gas Z can enter the individualmodules 7 only via the gas entry surfaces 14. Due to the conical inflowof the exhaust gas inflow area 5 created by the support element 11, auniform distribution of the exhaust gas to the four modules 7 occurs, asindicated by the corresponding arrows. After entering a module 7, theexhaust gas must pass through the entire length of the module 7 beforeleaving, purified, at the gas exit surface 15. The exhaust gas exits thehousing through the outlet 4 as exhaust gas A flowing out.

According to another exemplary embodiment of the invention, the supportelement 11 and the modules 7 installed therein can be arranged to form acentrosymmetrical formation, which eliminates the danger of an incorrector inverted installation of a prefabricated combination of supportelement 11 and modules 7.

The catalyst or filter elements shown in FIGS. 1 and 3 are layers thatcan be distinguished from one another. These layers are producedaccording to the prior art and connected to one another in a mannerknown to one skilled in the art. The metal foam body 8, which isupstream of the catalyst or filter elements, has an internal structurewith irregularly branched or labyrinthine channels and a porosity of 5to 20 ppi. Accordingly, exhaust gas striking the metal foam body 8 ishomogenized in the interior of metal foam body 8 and subsequently thedownstream catalyst and filter elements are uniformly flowed over.

It is noted that the foregoing examples have been provided merely forthe purpose of explanation and are in no way to be construed as limitingof the present invention. While the present invention has been describedwith reference to an exemplary embodiment, it is understood that thewords which have been used herein are words of description andillustration, rather than words of limitation. Changes may be made,within the purview of the appended claims, as presently stated and asamended, without departing from the scope and spirit of the presentinvention in its aspects. Although the present invention has beendescribed herein with reference to particular means, materials andembodiments, the present invention is not intended to be limited to theparticulars disclosed herein; rather, the present invention extends toall functionally equivalent structures, methods and uses, such as arewithin the scope of the appended claims.

1. A device for purifying exhaust gases from motor vehicles, comprising:a housing including an intake opening, an outlet opening, an exhaust gasinflow area, an exhaust gas outflow area, and a longitudinal axis; andat least one module for purifying exhaust gas arranged in the housingand having a module axis, wherein the at least one module connects theexhaust gas inflow area and the exhaust gas outflow area, and the moduleaxis is tilted relative to the longitudinal axis of the housing.
 2. Thedevice according to claim 1, wherein the module axis is tilted at anangle of 15° to 75° relative to the longitudinal axis of the housing. 3.The device according to claim 1, wherein the housing is substantiallycylindrical.
 4. The device according to claim 1, wherein the device is amuffler.
 5. The device according to claim 1, wherein the at least onemodule is made at least partially of metal foam.
 6. The device accordingto claim 1, wherein the at least one module comprises at least one of:at least one filter element and at least one catalyst element.
 7. Thedevice according to claim 1, wherein the at least one module comprisesseveral modules that are spaced apart from one another.
 8. The deviceaccording to claim 1, wherein the at least one module covers an entirecross section of the housing.
 9. The device according to claim 8,wherein the at least one module is connected to the housing.
 10. Thedevice according to claim 1, further comprising: a gas-tight supportelement connected to the housing to maintain the at least one module ina spaced apart relationship from the housing, and wherein the at leastone module penetrates the support element to allow the exhaust gas toflow between the exhaust gas inflow area and the exhaust gas outflowarea.
 11. The device according to claim 10, wherein the support elementis a metal plate.
 12. The device according to claim 10, wherein the atleast one module is substantially cylindrical and penetrates the supportelement with the module axis.
 13. The device according to claim 10,wherein the at least one module comprises plural modules that areencased in a gas-tight manner in some areas.
 14. The device according toclaim 10, wherein the support element is connected to the housing suchthat the exhaust gas inflow area is substantially conically tapered in adirection from the intake opening to the outlet opening.
 15. The deviceaccording to claim 1, wherein the device comprises at least one flowguidance device.
 16. The device according to claim 15, wherein the flowguidance device comprises a baffle plate.
 17. A method of purifyingexhaust gases of motor vehicles, comprising: directing exhaust gasthrough an inlet opening of a housing; purifying the exhaust gas in atleast one module arranged in the housing, in which the at least onemodule has a module axis tilted with respect to a longitudinal axis ofthe housing; and directing the exhaust gas through an outlet opening ofthe housing.
 18. The method of claim 17, wherein the module axis istilted at an angle of 15° to 75° relative to the longitudinal axis ofthe housing.
 19. The method of claim 17, wherein a gas-tight supportelement is connected to the housing to maintain the at least one modulein a spaced apart relationship from the housing, and the at least onemodule is supported to allow the exhaust gas to flow between the exhaustgas inflow area and the exhaust gas outflow area.
 20. The method ofclaim 19, wherein the support element is arranged in the housing to forma conically tapered exhaust gas inflow area.